Mobile metal melt contact system for the transmission of annealing currents

ABSTRACT

Moving metal stock of indeterminate length, such as tapes, wires, bars, tubes and the like, is annealed by the Joule effect of current passing therethrough from contacts applied to the stock at two spaced points. The stock moves over the contacts and so there is a problem of establishing and maintaining good electrical contact. The present invention provides as one of the contacts a fountain of molten metal that sprays against the underside of the stock. Molten metal is in electrical contact with a current source, and a motor-driven helical pump immersed in a bath of molten metal continuously provides the fountain.

United States Patent Prohaszka et al.

[111 3,861,658 Jan. 21, 1975 MOBILE METAL MELT CONTACT SYSTEM FOR THE TRANSMISSION OF ANNEALING CURRENTS.

[75] Inventors: Janos Prohaszka; Andor Mndoki;

Rudolf Welesz, all of Budapest, Hungary [73] Assignee: Licencia Talalmanyokat Ertekesito Vallalat, Budapest, Hungary [22] Filed: Mar. 26, 1973 [21] Appl. NO.: 345,201

[30] Foreign Application Priority Data 2,556,349 6/1951 Trautman 266/3 R 3,335,260 8/1967- Ferschl 266/3 R FOREIGN PATENTS OR APPLICATIONS 1,049,488 1/1959 Germany 200/195 1,063,698 8/1959 Germany Primary ExaminerRoy Lake Assistant ExaminerPaul A. Bell Attorney, Agent, or FirmYoung & Thompson [57] ABSTRACT I Moving metal stock of indeterminate length, such as tapes, wires, bars, tubes and the like, .is annealed by A the Joule effect of current passing therethrough from contacts applied to the stock at two spaced points. The stock moves over the contacts and so there is a problem of establishing and maintaining good electrical contact. The present invention provides as one of the contacts a fountain of molten metal that sprays I against the underside of the stock. Molten metal is in electrical contact with a current source, and a motordriven helical pump immersed in a bath of molten metal continuously provides the fountain.

3 Claims, 2 Drawing Figures Patented Jam.v 21, 1975 2 Sheets-Sheet 1 Patented Jan. 21, 1975 3,861,658

2 Sheets-Sheet 2 Fig.2

MOBILE METAL MELT CONTACT SYSTEM FOR THE TRANSMISSION OF ANNEALING CURRENTS For the annealing of semi-finished metal stock, finished stock of continuously moving metal or metal alloys, such as tapes, wires, bars, tubes to be used in a variety of technological processes, such as coating with molten metal, soldering, butt welding, heat treatment, etc. recourse is often had to the Joule effect of the current flowing through the material. In such and similar cases the selection of a system of contacts for the transmission of the current to the work may pose a problem difficult to solve. One method for this purpose is the transmission of current through rolling contacts, rollers, cylinders and the like. Another method is the conduction of the continuously moving work into a molten metal bath. In this case the current enters the product at the point of immersion in the metal bath. In the first instance difficulties may have to be overcome at the transmission of current between the contact rollers owing to the coarse, uneven, occasionally oxide-coated surfaces, or owing to the inevitable high surface load. In the second case the introduction of the workpiece into the metal bath and its subsequent removal from the bath give rise to design problems. As a matter of fact a system of conductors has to be designed which enables the immersion of tapes, wires, tubes, bars, etc. in the bath, and then their removal from the bath.

These problems have been solved by the molten metal contact system according to the invention. The new system of contacts permits the tapes, wires, bars, etc. to be annealed to advance on a roller or slide path, horizontally or nearly horizontally. The work passes over molten metal streaming from below upward, pouring through the orifice of a conduit, and then falling back into a basin. The metal streaming from below reaches and makes contact with the work, and drops then into the melt basin. There a pump drives the metal melt back to the site of contact. In this manner the continuously recycled molten metal establishes a definite, safe electrical contact with the work passing over the surface of the bath, without the immersion of the work in the bath. At least one pole of a current source is connected to the molten metal contact, the other pole being connected to a second molten metal contact or to a conventional contact, the use of even one contact according to the present invention improving the performance. The circuit is thus completed through the work, with the following advantages:

1. Better contact and current transmission are achieved than in the case of purely mechanical, or the known molten metal immersion systems. Current transmission to a rapidly moving workpiece having perhaps a roughened surface and even a complicated crosssectional configuration, is much more certain with the aid of the molten metal contact of the present invention than with a purely mechanical contact. Also, as compared to earlier known molten metal contacts, current transmission is more certain with the present invention because the moving molten metal of the present invention prevents impurities from adhering to the workpiece. Also, according to the invention, current transmission and also the contact between the workpiece and the molten metal, may be limited to a short path and a small area, respectively. Thus the workpiece heated by the Joule effect will transmit only a moderate amount of heat to the molten metal, so that the molten metal will not become overheated. This has the advantage that excessive evaporation and oxidation are avoided.

2. Known systems of contacts operating with molten metal required that the workpiece be flexible so that it could be immersed in the bath. There was no way to immerse relatively rigid material in the bath. But with the present invention, workpieces of all sizes, shapes and rigidity can be treated.

These and other features and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 is a somewhat schematic side elevational view of an installation according to the present invention; and

FIG. 2 is an enlarged fragment of the fountain bath shown in FIG. 1.

Referring now to the drawings in greater detail, there is shown an installation according to the present invention, in which metal strip 1 passes over an'entry roll and is collected by winding on a final roll 2. Strip 1 passes through opposed contact rolls 3 of a conventional nature which serve as one electrical contact; and a relatively short length 4 of strip 1 emerging from rolls 3 then passes through the second or other contact 5 and thence through graphite wiping members 6 by which any remaining molten metal is removed. The strip then moves into a work station 7 in which an operation such as cooling or the application of printed circuitry or other further work operations may be performed on the strip, prior -to rolling the stripon the roll 2.

A current source 8 is connected at one pole through conventional brushes 9 to one of the rolls 3 and at the other pole to contact 5. The stand for the rolls 3, like that for the contact 5, rests on an electrically insulating base 10.

Further details of the contact 5 are shown in FIG. 2. In FIG. 2, the strip is shown passing above a housing 11 which defines a bath 12 of electrically conductive liquid, preferably molten metal such as molten lead. Heating elements 13 may be provided to maintain the bath of liquid at the desired temperature.

Immersed in the bath I2 is a fountain projector 14 for molten metal or other electrically conductive liquid, comprising a discharge nozzle 15 fed by a screw conveyor 16 driven in rotation by a motor 17. Molten metal is drawn in through the casing of projector 14 through openings 18, and is discharged upwardly against the underside of the strip 1, whence it falls back down to the bath 12, the electrical circuit being maintained through the continuous upwardly moving stream of molten metal to the strip 1 and thence through portion 4 of the strip to the associated roll 3 and through brush 9 to current source 8.

The area of the strip I bathed by the molten metal is confined by asbestos rings 19 supported by housing 11 and a circular cover 20.

Thus for example, for the annealing of a manganese steel strip of 0.20 percent carbon content, of the Hungarian standard CS2, with a width of 10 mm. and a thickness of 1 mm., it is suitable to position the contacts 3 and 5 apart by a distance of 2 meters, and to employ a bath 12 of 200 kg. of molten lead, an orifree 5 mm. wide for nozzle 15, and to direct the lead against the underside of the moving strip positioned 15 mm. above the surface of bath 12, with a velocity sufficient to bathe a length of strip of 60 mm. The current source 8 may supply current at 40 volts and 180 amps,

' and the terminal for contact may be immersed in bath 12 as shown in FIG. 1 or secured to housing 11 as shown in FIG. 2, the length 4 of strip 1 attaining a temperature of 700C. in either case. The strip speed of course predetermines the annealing time.

Although the present invention has been described and illustrated in connection with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Such modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

Having described our invention, we claim:

1. In apparatus for annealing a continuous moving length of metal, comprising means establishing electrical contact with said metal at a pair of points spaced apart a substantial distance in the direction of movement of the metal, and means for passing an electric current from a source of current through said metal between said contact means; the improvement in which at least one of said contact means comprises a quantity of electrically conductive liquid in electrical circuit with said source of current, means to project said liquid upwardly in a fountain against the underside of said metal, said fountain projecting means comprising a pump having an upwardly directed outlet, and power means to operate said pump.

2. Apparatus as claimed in claim 1, and means to collect said quantity of liquid in a bath back to which the liquid of said fountain falls by gravity after contacting said metal, and means for supplying liquid from said bath to said fountain.

3. Apparatus as claimed in claim 1, said pump comprising a vertical cylindrical casing housing a helical worm, said power means rotating said worm. 

1. In apparatus for annealing a continuous moving length of metal, comprising means establishing electrical contact with said metal at a pair of points spaced apart a substantial distance in the direction of movement of the metal, and means for passing an electric current from a source of current through said metal between said contact means; the improvement in which at least one of said contact means comprises a quantity of electrically conductive liquid in electrical circuit with said source of current, means to project said liquid upwardly in a fountain against the underside of said metal, said fountain projecting means comprising a pump having an upwardly directed outlet, and power means to operate said pump.
 2. Apparatus as claimed in claim 1, and means to collect said quantity of liquid in a bath back to which the liquid of said fountain falls by gravity after contacting said metal, and means for supplying liquid from said bath to said fountain.
 3. Apparatus as claimed in claim 1, said pump comprising a vertical cylindrical casing housing a helical worm, said power means rotating said worm. 